1. Field of the Invention
The present invention relates to a method and a device for testing an image sensor and to a motor vehicle.
2. Description of the Related Art
When image sensors are used in safety-critical applications, such as driver assistance systems or evasive steering support systems in motor vehicles, it is necessary to test the image sensor to ensure its correct functional capability.
Within the meaning of the present invention, image sensors include pixels and a signal processing unit for providing digital signal values of the pixels. A portion of the pixels, the so-called test pixels, is connected in each case to one of two predefined voltage values. The remaining, regular pixels put out voltages as a function of the intensity of the light incident upon the particular pixel. The pixels are usually arranged in a matrix made up of rows and columns.
One option for testing an image sensor involves evaluating associated signal values of the regular pixels with respect to a test pattern. The image sensor may include an internal memory, for example, to which the test pattern may be temporarily written or permanently written. Moreover, the image sensor may be designed so that one or more reference voltages may be applied to the pixels.
While the image sensor is being tested, no regular image output may take place, i.e., no regular image signals may be provided from digital signal values which are determined by the instantaneous incident light. Tests of the image sensor are therefore carried out during start-up, during maintenance or in the idle state of the image sensor.
For end-of-line calibration or other purposes, test pixels are sometimes provided in image sensors, which are fixedly interconnected with one of two predefined voltage values, instead of varying their output voltage as a function of the incident light.